This application is a 371 of PCT/GB99/02437 filed Jul. 9, 1999.
This invention relates to liquid formulations of pyrimethanil and methods for their preparation. In particular, the invention relates to suspension concentrate (SC) formulations that contain high proportions of solid pyrimethanil.
Commercial SC formulations comprising the fungicide pyrimethanil include Mythos(copyright) and Scala(copyright). Typically these formulations contain not more than 40% w/v pyrimethanii. Increasing the amount of pyrimethanil in these formulations above 40% would be advantageous, since it would reduce the cost of transporting a given amount of active ingredient. These savings would be particularly significant where pyrimethanil is transported to remote places where distribution is difficult, such as to tropical zones. However, increasing the concentration of pyrimethanil in these formulation leads to milling problems during manufacture and crystallisation during storage.
It is therefore an object of the invention to devise an SC formulation system containing concentrations of pyrimethanil significantly greater than 40% without experiencing the abovementioned problems.
According to a first aspect, the invention provides an aqueous SC formulation comprising a) 50 to 80% w/v pyrimethanil, preferably 60 to 80% w/v; b) 0.2 to 5% w/v of a polyoxyethylene-polyoxypropylene block copolymer surfactant, preferably 0.3 to 1.5%; and c) 0.2 to 5% w/v of a napthalene formaldehyde condensate surfactant, preferably 0.3 to 1.5%.
We have found that formulations according to the invention surprisingly do not solidify when milled during manufacture and also exhibit a low propensity to crystallise when stored for prolonged periods.
Throughout this specification, unless the context requires otherwise, the word xe2x80x9ccomprisexe2x80x9d, or variations such as xe2x80x9ccomprisesxe2x80x9d or xe2x80x9ccomprisingxe2x80x9d will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers including method steps.
Preferably component b) has a molecular weight of 6000 to 14000, especially 9000 to 13000. Further, component b) contains 20 to 80% w/w of polyoxyethylene, especially 40 to 80%. In particular, the molecular weight of component b) is nominally 12000 and the amount of polyoxyethylene is nominally 70% w/w.
Preferably component c) is a salt, particularly the sodium salt.
Preferably the formulation also comprises a dispersant, such as a polymethyl methacrylate-polyethylene glycol graft copolymer, preferably having a molecular weight of 20000 to 30000, in amounts of 1 to 10% w/v, preferably 3 to 8%.
A particularly preferred SC formulation comprises a) approximately 60% w/v pyrimethanil, b) approximately 0.5% w/v of an ethenylenoxy-propyleneoxy block co-polymer surfactant, c) approximately 1% w/v of sodium naphthalene formaldehyde condensate surfactant, d) approximately 5% w/v polymethyl methacrylate-polyethylene glycol graft copolymer, e) approximately 6% w/v propylene glycol and f) approximately 37.5% w/v water.